Variant espgene as a marker of a distinct genetic lineage of vancomycinresistant Enterococcus faeciumspreading in hospitals

In the USA, vancomycin-resistant Enterococcus faecium(VREF) is endemic in hospitals, despite lack of carriage among healthy individuals. In Europe, however, hospital outbreaks are rare, but VREF carriage among healthy individuals and livestock is common. We used amplified fragment-length polymorphism analysis to genotype 120 VREF isolates associated with hospital outbreaks and 45 non-epidemic isolates from the USA, Europe, and Australia. We also looked for the espvirulence gene in these isolates and in 98 VREF from animals. A specific E faeciumsubpopulation genetically distinct from non-epidemic VREF isolates was found to be the cause of the hospital epidemics in all three continents. This subpopulation contained a variant of the espgene that was absent in all non-epidemic and animal isolates. Identification of the variant espgene will be important in guiding infection-control strategies, and the Esp protein could be a new target for antibacterial therapy.